Talk about bad timing! Prankster Alexander Bok picked on the cops just as the entire department is grieving over the assassinations of two patrolmen last week.

With tension in the city at an all-time high, angry cops even turned their backs on Mayor Bill de Blasio at a funeral on Saturday because they view him as siding with protestors. They also booed him at a Police Academy graduation on Monday.

The idea for the dancing prank came from Ellen DeGeneres in a recent show. She declared, "I am bringing back, by popular demand, too. A few seasons ago we did something called 'Dance Dares' where I challenge the viewers to sneak up behind perfect strangers."

Bok accepted the challenge and started dancing behind a whole bunch of strangers at New York’s Grand Central Station. Most people were amused. But when he tried it with the cops the joke was on him. They turned the prankster around and started to frisk him. They soon let him go but one cop seemed to shove him.

A cop told Bok, “Take a [expletive] walk!”

Police say they are reviewing the incident.

Security expert Steve Kardian watched the video and said, "How stupid can a person be to do that in light of what has occurred in New York City? To go up behind a New York City police officer and do this kind of motion."